1. Field of the Invention
The invention is a drive apparatus for hard disk memories with an integrated labyrinth seal.
2. Description of the Related Art
An arrangement of the general type of this invention is known from German patent publication 30 49 334 C3, for example. In this known apparatus, a series of labyrinth gaps are designed, namely a first labyrinth gap in the upper area of a rotating shaft, which is fastened securely to a rotor cap, and also in the lower region across from a stationary support flange.
Due to existing manufacturing inexactness, it is very difficult to design such seals to be very long and narrow due to the dimensioning and arrangement of the labyrinth seal since the danger exists of the rotor cap colliding with the stationary parts of the support flange.
A primary purpose of the invention is to develop a drive apparatus of the above-named type such that with the same manufacturing accuracyxe2x80x94as with the state of the technologyxe2x80x94considerably more narrow seal gaps can be achieved.
An important feature of the invention is that a bell-shaped rotor cap has an annular flange directed radially inward whose inwardly radial face forms the lower seal gap together with the stationary shaft, while a separate upper seal, a somewhat disk-shaped part, is solidly connected to the rotor cap at a distance from the lower seal gap and likewise forms an upper seal gap with its inward radial surface parallel to the shaft.
A considerable advantage arises from the technical theory provided in that the upper and lower seal gaps according to the invention are formed on very exactly machined surfaces on the stationary shaft. The advantage thus arises that only the shaft has to be exactly machined and is designed as a stationary shaft, while upper and lower seal gaps encompassing this stationary shaft are formed by seal surfaces from circular elements of the rotor cap directed radially inwardly.
The upper and lower seal gaps proposed here lie as close as possible radially inwardly to the shaft and thus have a very small diametric clearance. The gaps themselves have a dimension of approximately 10 to 20 xcexcm (micrometers) and lie, as stated, at the maximum radial inward position in the entire arrangement, which was not the case in the state of the technology. The concept of xe2x80x9csealxe2x80x9d should not be narrowly defined here. All seal constructions fall under this category, especially labyrinth seals, or cylindrical, barrel-shaped or other types of profiles or also flat annular seals having non-touching opposing seal surfaces.
In the state of the technology, the named seal gaps had a large radial separation from the rotating shaft which had the disadvantage that an out-of-round condition had to be smoothed out. Corresponding machining errors had a negative effect on the characteristics of motion to a great extent (due to the separation from the center of rotation) such that large seal gaps were required for safety reasons. This problem is obviated by the structure of the present invention.
In a preferred embodiment of the invention, it is provided that the rotor cap has an upper opening somewhat cylindrical opening into which the seal is fitted in a pressed seat so that the part of the seal on the outer radius lies against the inner wall of the opening in the rotor cap in a pressed seat (or also using adhesive) and thus is fastened solidly to the rotor cap. The surfaces of this seal directed radially inward form the upper seal gap in connection with the shaft on the inside.
In the same way, the rotor cap has a lower annular flange directed radially inward which also forms the lower seal gap with its radially inwardly directed surfaces and the shaft. The rotor cap also has inner housing space to house the stationary portion (stator) of the motor in a known fashion.
A further important advantage arises with the apparatus of the invention in that a simple assembly is possible. First, the shaft with the upper and lower ball bearings and the spacer in between is pre-assembled and pre-clamped so that the two ball bearings are tensioned against one another with no play. The ball bearings are tensioned by an external force (for example by a weight) against one another with no play and then are bonded to the shaft. The metal seal is then set on the pre-stressed and solidly held bearing arrangement and fastened, after which the rotor cap is clinched from below over the arrangement. The rotor cap is heated, giving it a larger inside diameter. When it cools the rotor cap sits against the pressed seat on the outer circumference of the seal. At the same time the lower edge of the lower ball bearing pushes against the radially inwardly-directed annular flange of the rotor cap so that this is aligned correctly with the shaft.